1. Technical Field
The present disclosure relates to electrosurgical instruments used for open and endoscopic surgical procedures for sealing or fusing tissue. More particularly, the present disclosure relates to a bipolar forceps for sealing vessels, vascular tissues and soft tissues having an electrode sealing assembly which is designed to limit and/or reduce thermal spread to adjacent tissue structures by rapid cooling.
2. Background of the Related Art
Open or endoscopic electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis. The electrode of each opposing jaw member is charged to a different electric potential such that when the jaw members grasp tissue, electrical energy can be selectively transferred through the tissue. A surgeon can cauterize, coagulate/desiccate and/or simply reduce or slow bleeding, by controlling the intensity, frequency and duration of the electrosurgical energy applied between the electrodes and through the tissue.
Certain surgical procedures require more than simply cauterizing tissue and rely on the combination of clamping pressure, electrosurgical energy and gap distance to “seal” tissue, vessels and certain vascular bundles. More particularly, vessel sealing or tissue sealing utilizes a unique combination of radiofrequency energy, clamping pressure and precise control of gap distance (i.e., distance between opposing jaw members when closed about tissue) to effectively seal or fuse tissue between two opposing jaw members or sealing plates. Vessel or tissue sealing is more than “cauterization”, which involves the use of heat to destroy tissue (also called “diathermy” or “electrodiathermy”). Vessel sealing is also more than “coagulation”, which is the process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” is defined as the process of liquefying the collagen, elastin and ground substances in the tissue so that the tissue reforms into a fused mass with significantly-reduced demarcation between the opposing tissue structures.
Using electrosurgical instruments to seal tissue may result in some degree of so-called “thermal spread” across adjacent tissue structures. “Thermal spread” refers generally to the heat transfer traveling along the periphery of the electrically conductive surfaces. This can also be termed “collateral damage” to adjacent tissue. As can be appreciated, reducing the thermal spread during an electrical procedure reduces the likelihood of unintentional or undesirable collateral damage to surrounding tissue structures which are adjacent to an intended treatment site. Reducing the collateral damage to surrounding tissue or maintaining the viability of surrounding tissue after the sealing process is known to promote tissue healing and decrease overall healing time by stimulating/improving healing response.
Controlling tissue cooling may also reduce adhesion or buildup of tissue on the electrodes and also assist during the formation of the tissue seal, e.g., cross-linking or other chemical bonding, during the reformation or renaturation of collagen. In existing sealing devices this cooling takes place in a natural-passive-way (due to heat exchange with the environment) after energy application is stopped. The cooling rate in this case is determined by thermal properties of the tissue and the jaw members and by the arrangement of heat exchange between jaws and the environment.